This invention relates to a seated-operator type tractor. Although various devices for improving safety with respect to working function of the tractor of this type have been contrived and conventionally been in use, no sufficient consideration has so far been paid in securing the safety of the operator in case of accident such as turnover of the tractor body, in spite that the tractor has considerable weight and is not very stable with the construction of rather high center of gravity, perhaps under excuse that the tractor generally travels in slow speed. There has thus been a potential danger of detrimental disaster such as crushing the operator under the tractor body if it should by any chance so badly lose stability as to overturn on heavily irregular ground such as rough slope.